This invention relates to electronic semiconductor devices and, more particularly, to an acoustic charge transport technique and delay device that is compatible with integrated circuit technology and which has applications including filtering, convolution, correlation, and other signal processing functions which employ delay elements. The device hereof also has application as an analog register and a video signal generator.
Surface acoustic wave ("SAW") devices have been developed to provide reasonably low cost and power-efficient devices for use as delay lines and filters, and in other signal processing applications. However, a difficulty with "SAW" devices is that they are generally implemented on dielectric substrates that tend to be incompatible with existing integrated circuit technology. This makes it difficult to combine the gain and control capability of integrated circuit semiconductor technology with the high computational speed of "SAW" devices to get cost-effective monolithic signal processors.
Devices which are generally compatible with integrated circuit technology, and which are useful in the above-mentioned types of applications are charge-coupled devices ("CCD"). CCD's are being developed on different types of substrates including silicon and gallium arsenide, and great advances have been made in CCD technology in recent years. However, CCD's require a large number of closely spaced gates and associated connections, along with clock driver circuitry. Operation of CCD's at high speeds remains difficult.
It has been previously recognized that "SAW" devices could be used in conjunction with silicon wafers to obtain travelling potential wells in the silicon, and that signal charge could be injected into the potential wells. However such devices can exhibit charge transport inefficiency due to carriers being dragged along a surface and surface states trapping some of the carriers as they go by.
It is among the objects of this invention to provide an improved charge transport device and technique that is compatible with integrated circuit technology and exhibits good charge transport efficiency.